This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Different sizes of silicon particles with porous nanostructure and intrinsic photoluminescence are prepared and studied. Their low toxicity and biodegradability also give the particles great potential for biological applications. Using the photoluminescent porous Si particles for diagnostic and therapeutic applications are under study.